For a silicon wafer used as a material for producing a semiconductor device, a substrate obtained by slicing a silicon single crystal grown by the Czochralski (CZ) method, in particular, the Magnetic field applied Czochralski (MCZ) method that produces a crystal while applying a magnetic field, the substrate with a polished surface, is used. In recent years, a wafer without slight projections and depressions has been required as the quality of the surface of such a wafer as the design rules in the production of the semiconductor device have become finer. This has become an increasingly important quality item for monitoring a break by slight projections and depressions and a foreign substance in a device production step because the size of wiring in device production has become finer. For evaluation of the quality of such a silicon wafer surface, a laser particle counter is used, and the detection size of a particle has increasingly become finer and has become 45 nm or less as the design rules of the device have become finer. Therefore, preventing a micro defect caused by processing in a mirror processing (polishing) step of a wafer surface and a minute foreign substance and impurity in wafer cleaning which is a post-step of the mirror-like finishing (polishing) step has been performed.
On the other hand, it is well known that, when a COP (Non-patent Literature 1) is present on the silicon wafer surface as a crystal defect and a concave indentation is formed on the wafer surface, this is measured as an LPD by a laser particle counter. That is, what is not an actual foreign substance is sometimes detected as a particle. It has been reported that these crystal defects are formed in accordance with a temperature gradient (G) and a growth rate (V) during crystal growth (Non-patent Literature 2). Moreover, a production method in which these G and V are controlled, for example, in Patent Literature 1, a method for controlling the formation of a crystal defect by reducing the growth rate of a silicon single crystal has been reported. Furthermore, in Patent Literature 2, it has been reported that a defect-free crystal containing practically no COP can be obtained by pulling a single crystal at a rate (V) that does not exceed the maximum pulling rate of a single crystal that is approximately proportional to a temperature gradient (G) in a boundary region between a solid phase/a liquid phase of a silicon single crystal.
Moreover, it is also disclosed that, in a step of mirror processing a wafer, a PID (Polished Induced Defect) formed as the effect of a residue at the time of polishing is detected as an LPD of a silicon wafer (Patent Literature 3). It has been reported that the LPD (PID) caused thereby is improved by a chemical solution used at the time of polishing and by a cleaning step.
However, even a silicon wafer obtained by slicing a defect-free silicon single crystal in which no COP is present, the defect-free silicon single crystal grown by such a production method as disclosed in Patent Literature 2, the silicon wafer produced by a step in which a PID in the polishing step is not generated, when the detection size of a particle is made finer and is set at 45 nm in a laser particle counter, an LPD is sometimes detected. That is, even in a wafer with a wafer surface in which no foreign substance is actually present, the wafer in which neither COP nor PID is present, when the detection size in particle measurement is made finer and then a quality inspection is performed, LPDs may be detected in high density, the wafer may be judged to be a failure in an inspection step and a shipment stage of the wafer, and yields may be reduced.